This invention relates to liquid crystal displays adapted for timepieces, especially solid state analog timepieces having radial "hands" to display the time.
Conventional liquid crystal displays have front and rear transparent substrates with transparent electrodes or segments arranged to display information when actuated by signals from an electrical circuit. Liquid crystal displays of various types are well known in the art and, for example, may include liquid crystal material sealed between the substrates, and associated with one or more polarizers to provide the well-known twisted nematic, field effect, liquid crystal display.
Conventional liquid crystal displays are arranged with the contact terminals on the periphery of the display, usually on the underside an over-hanging edge of the top substrate as seen in U.S. Pat. No. 3,863,436--Schwarzschild, et al issued Feb. 4, 1975. Contact terminals have also been provided at the edges of the display as shown in U.S. Pat. No. 4,391,531--Yokota et al issued July 5, 1983. Both of these patents are assigned to the present assignee.
Liquid crystal displays with radial "hands" representing mechanical hour, minute and second hands have been proposed as seen in U.S. Pat. No. 3,540,209 to Zatsky, et al issued Nov. 17, 1970; and in British Patent Specification No. 1,472,260, these being merely exemplary. Timepieces using radial hand liquid crystal displays are sometimes called solid state analog or liquid crystal analog timepieces.
When constructing a liquid crystal display for a timepiece with radial members, it is desirable to use as much of the outer part of the display surface as possible, so that the "hands" can extend as far as possible from the center for ease of readability. The conventional placement of contact terminals on the outside edges of the display, especially when using the technique requiring an overlapping edge on the top substrate, reduces the effective display area which is available for visible segments. It would also be desirable to have more flexibility at the outer periphery of the display to use round, octagonal, oval or other shapes of display than rectangular.
Liquid crystal displays for solid state analog timepieces have been proposed in which the integrated circuit and quartz crystal were disposed on the underside of the upper display substrate. The proposed construction is described in Inter Electronique, dated Dec. 11, 1972, pages 33-36. Such an arrangement naturally leads to a very large central opening and difficult construction.
It has also been suggested to provide a liquid crystal display for a digital timepiece combined with mechanical analog hands carried on a stem extending through a central hole in the display. Such an arrangement is shown in British Published Patent Application No. GB 2 084 764A--Maliska, published Apr. 15, 1982, assigned to the present assignee.
Accordingly, one object of the present invention is to provide an improved liquid crystal display for a solid state analog timepiece which increases the availability of display area at the outer part of the display.
Another object of the invention is to provide an improved liquid crystal display with improved means to connect the display to an external circuit which permits greater flexibility to choose the shape of the display.